What is Dopamine?
Dopamine is a neurotransmitter within the brain and body that plays important roles in emotion, motor control, focus maintenance, working memory, and is involved in reward and pleasure pathways. Imbalanced dopamine can be implicated in addiction, depression, apathy, Parkinson’s disease, ADHD, schizophrenia, and psychosis.
What is Testosterone?
Testosterone is a sex hormone (primarily produced in the gonads and secondarily produced in the adrenal glands) that is involved in libido, vitality, bone density, fat distribution, muscle strength and mass, face and body hair, the production of sperm in males, and the production of red blood cells. Imbalanced testosterone can lead to decreased sexual desire, changes in sleep, reduced muscle mass, and decreased self-esteem (Sexual Health, Mayoclinic).
Dopamine and Testosterone: A Bidirectional Relationship
What do these two organic substances have in common? One big area where they share a significant relationship and play a crucial role in health is in male sexual function. The relationship between dopamine and testosterone is bidirectional: dopamine can influence testosterone and testosterone can influence dopamine. In males, an important area of the brain for sexual function is the medial preoptic area.
One study found that microinjecting dopamine agonists (which increase dopamine function) in the medial preoptic area of rats resulted in an increase of sexual activity (Dominguez et al. 2005). Another study observed that castrated male rats showed no interest in fornicating and no dopamine release in the medial preoptic area. After testosterone injections, the castrated rats were able to engage in sexual intercourse and showed an increase in dopamine release in the medial preoptic area (Putnam et al. 2001).
These studies demonstrate how dopamine is important for libido and how testosterone regulates its release in the medial preoptic area. But as stated above, the dopamine-testosterone relationship is not one-sided.
The Hypothalamic-Pituitary-Gonadal Axis
The production of testosterone is controlled via a specific feedback loop called the hypothalamic-pituitary-gonadal axis. The hypothalamus secretes a gonadotropin-releasing hormone (GnRH), which signals the pituitary gland to secrete luteinizing hormone (LH), which in turn signals the gonads to produce testosterone.
One study observed the impact that dopamine has on GnRH production, and thus testosterone production. Researchers found that the administration of a dopamine agonist in rat brains increased the amount of GnRH mRNA by 67%, which is involved in the DNA replication of GnRH (Li et al. 1992). Thus, adequate dopamine function is necessary for the production of testosterone.
Consult Your Doctor About Your Dopamine & Testosterone
If you are a male who is suffering from low libido, in addition to correcting any testosterone imbalances, it is also important to see if low dopamine is a contributing factor.
Talk to your doctor about having your neurotransmitter levels assessed. If dopamine is low and poor sex drive is present, correction using targeted nutritional therapy may help to restore levels and support a healthy sex life.
Dominguez JM, Hull EM. Dopamine, the medial preoptic area, and male sexual behavior. Physiol Behav 2005;86: 356-368
Li S, Pelletier G. Role of dopamine in the regulation of gonadotropin-releasing hormone in the male rat brain as studied by in situ hybridization. Endocrinology 1992;131(1):395–399.
Putnam SK, Du J, Sato S, Hull EM. Testosterone Restoration of Copulatory Behavior Correlates with Medial Preoptic Dopamine Release in Castrated Male Rats. Hormones and Behavior 2001;39(3):216–224.
Sexual health. Testosterone therapy: Potential benefits and risks as you age. Available at: http://www.mayoclinic.org/healthy-lifestyle/sexual-health/in-depth/testosterone-therapy/art-20045728. Accessed March 4, 2016.